Art of pressure distillation



E. M. CLARK.

ART OF PRESSURE DISTILLATION.

APPLICATION FILED "ML 31, I919.

; Patented Jam 31, 1922;

UNITED s -Ares PATENT OFFICE,

EDGAR M. CLARK, or NEW YORK, N. Y., ASSIGNOR T STANDARD OIL COMPANiLlOF" NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

, .ART OF PRESSURE DISTI-LLATION'.

Application filed March '31, 1919. Serial No. 286,263.

To aZZ whbmit may concern v Be it known that I, EDGAR-M. CLARK, a

I citizen of the United States, residing at New York, in the county of New York and State of New York, have invented a new and useful Improvement in the Art of Pressure Distillation, of which thefollowing is a specification. 0 My present invention relates to the art 0 pressure distillation of heavy petroleum oils as conducted for the'purpose of converting such oils by pyrogenesis into lighter oils of the character of gasoline. The invention will befully understood from the following specification taken in connection with the accompanying drawing, which represents a side elevation, partly in section, of a pressure-cracking still of the tubular type and built in accordance with the principles of this invention.

Referring more particularly to the drawing, the numeral 1 designates the drum of the still, this drum, as shown, being of horizontal cylindrical form and supported above Above the still-drum there is mounted a' I vapor drum 7, also preferably of-horizontal cylindrical form as illustrated, and supported and connected with the still at one end by a vapor pipe 8, the opposite end being supported by a roller 9 resting upon the top of ,the still-drum. By this method of mounting the vapor drum, the strains due to. the expansion and contraction of the parts are reduced to a minimum. Near one end of the vapor drum 7 the latter is provided with a transverse tube sheet 10 in which there are secured two horizontal rows of tubes, the upper row being designated 11 and the lower row 12. All of the tubes are provided with small perforations for the escape of vapors as will later appear, the upper row 11 being capped at the outer end as shown at 13, while the lower row 12 has 'downturned elbows and nipples, as shown at 14. Spaced away from the tube sheet-10 there is a false head 15 which. terminates short of the upper side of the vapor drum to leave a free vapor passage 16 over its upper edge. Anoverflow pipe 17 passes through" the false-head 15 and is fastened to the tube sheet 10 some distance below the top of the drum. The horizontal leg of this overflow pipe is connected by an elbow with a vertical leg 17 which extends downward centrally through the vapor connection 8 and terminates near the bottom of the stilldrum 1 and preferably just above the opening of the rear or longer leg 6. A dam 6' extends transversely of the'bottom of the vdrum in front of the leg 6. A direct passage feed pipe 19 is tapped into the other or lefthand end ofthe drum as seen on the drawlng and a draw-01f pipe 20 into the bottom of the drum near the tube sheet 10. The

draw-off pipe or tar-line of the still is designated 21 and is preferably tapped into the lowest point of the still which is the bottom of the lower tube header 5.

Both the still drum and the vapor drum are provided with manheads at theends and top and with gauge glasses as shown. There will also be the customary equipment of pressure gauges and pyrometers or high-temperature thermometers for taking the temperatures and pressures within the vapor drum and still drum.

A vapor pipe 22 is tapped into the top of the vapor drum and leads to a condenser (not illustrated). Preferably, the still illustrated by the present drawing will form one of a battery, all of the stills in the battery having theirindividual water-cooled condensers connected with the vapor-lines 22 and through the'latter with the receivinghouse equipment illustrated inv my prior Patent No. 1,132,163, it being understood that the still represented by the present drawing is to be substituted for the type of still illustrated and described in the said patent. I A

In the conduct of the distilling operation employing the apparatus above dethat the'vapor drum between the tube sheet 10 and the far end and up to the level of the overflow-pipe 17 has a capacity of 6,000 gallons. At the beginning of the operation, the still and drum will be charged with the named amounts of gas oil from mid-continent crude petroleum, for example, a 32 E,

oil. The still will now be fired and raised to a temperature of, for example, 400 F.

. while under atmospheric pressure. During this initial heating, any traces of water and of lightoils which may be present in the gas oil will distill over freely through the water-cooled condenser (not shown) and be evacuated from the system. "When atemperature of about 400 F. has been attained, the receiver of the still will be connected through the means shown in my prior patent referred to with the high-pressure gas line, and by this means the free spaces in the condenser, still and drum will be charged with petroleum oil gas up to the operating pressure, for example, 95 pounds per square inch. It ivill be noted that this gas enters the vapor drum through the vapor line 22, and by reason of the check valve 18 is permitted to pass directly from the vapor drum into the still 1. The operating pressure having thus bee-n established in the apparatus, firing of the still will be continued until the temperature of the oil body in the still reaches about 725 to 728 F. At this temperature, decomposition of the gas oil in the still 1 will proceed rapidly, the gasoline vapor thus generated will pass out through the vapor connections 8 over the top of the false-head 15 and by displacing the oil between the tube-sheet and false-head will enter therows of tubes 11 and 12 and escape from the latter, bubbling through the deep liquid body in the vapor drum. In the earlier stages of the operation, there will be almost complete condensation of the vapors in their passage through this liquid body, such condensation adding to the volume of the liquid in the drum and causing it to overflow back into the still. lVithin a short time the transfer of heat from the still to the vapor drum in this fashion, raises the temperature of the oil in the vapor drum to about 510 at which point the gasoline'vapors will pass unchanged through the oil body, only those distilled fractions from the oil in the still which are substantially heavier than gasoline being condensed by bubbling through the oil in the vapor drum. The gasoline vapors will pass continuously out through the vapor-line 22 to be condensed in the water-cooled condenser (not shown), and evacuated from the receiving drums in the receiving house, as described in my prior patent referred to, the pressure being meantime constantly maintained at the predetermined figure by the open connection between the still the 95-pound gas-line. he normal initial running condition the OlVS f atus therefore will be substantially mosses Vapors ofgasoline mixed with a very considerable proportion, amounting perhaps to densed and overflowing back to the still' through the pipe 17,- y

When these normal running conditions have been established, the still will be fired as such a rate as to produce approximately 320 gallons of distillate per hour, which distillate may have a gravity of 57 B. and a maximum boiling-point'of 500 l. The introduction of fresh stock into the vapordrum 7 through the feed pipe-19 will now be begun, such fresh stock being fed at the same rate at which the distillate is produced so that the total volume of oil within the system remains constant. The stock thus in-fed maybe the same as that originally charged, that is, 32 B. mid continent gas-oil, or it may be a lighter oil, for example, an oil of 86 B. of the same general character. As a varient of the process the stock fed to the vapordrum may be a medium heavy crude distillate containing -a considerable percentage of naphtha fractions, for example, the crude cut known as light parafiin gas-oil and containing up to 20% naphtha fractions produced by cracl ring at atmospheric pressure in the later stages of the run in the fractional-distillation of crude petroleum. If such light paraffin gas-oil be employed as a feed stock, the naphtha fractions thereol will be immediately vaporized upon the entrance of the oil into the vapor drum, the drum serving as a skimming still for this purpose. llt will be understood that if this variation of procedure is restorted to, the naphtha'fraction of the infed stock must be accounted for in governing the teed rate and distillation rate. I

A normal run under the conditions de scribed will be completed in 60 hours, the distillate being taken over at the rate of 320 gallons per hour during that time and feed stock bein introduced at the same rate. Thus, the total gallonage or the stock chargedand ted will be 38,200 and the total distillate taken or? 19,200 or approximately 50%. At the end of the run there will remain in the still 13,000 gallons ct relatively heavy tar, for example, 18 :8, while there will be in drumhfifiti ga -..s o intermediate oil a avity of 38 ing in its entirety a om colre or suspenduse as a stool-i,

a considerable percent 1 recovered.

age of fractions within the heavy naphtha and refined oil or kerosene'range may be I. have found, under the conditions of operation described, that loss of heat from the vapor drum 7, together with the heat absorption of the cold infed stock, will generally be sufficient to maintain the desired temperature of approximately 510 F. with in the drum. The temperature may be maintained at a lower figure, however, and accurately controlled by constantly withdrawing any desired amount of oil from the vapor drum by the pipe 20, passing this oil through a cooler and feeding it again to the drum at the same rate at which it is withdrawn. It is to be noted, with respectto the process described in the foregoing,

that the temperature within the still, assuming a constant distillation rate and a constant gravity. of distillate, remains substantially uniform throughout the run. Thus,

in the example given, the temperature may be expected to remain between the limits of 725 to 728 F., with careful firing.

It is also to be noted that the continuous refluxing of the oil from the drum into the still, together with the continuous feeding of the drum, is made to benefit the operation of the still itself byreturning this reflux in such a position that it passes immediately to the tube bank 2, diluting the tar or heavy oil of the still-drum -asthe latter enters the rear conduit 6 in its thermo-siphon circulation. As a result of such continuous dilution, several beneficial effects are obtained, i. e., the deposition of carbon within the tubes 4 is lessened, and the deposition of carbon within the drum 1 is increased, both byreason of the greater relative density of the tar in this drum and because of the slow circulation of the oil through it. The dam 6 is of further aid in preventing deposition of carbon'in the tubes in that it gives a better opportunity for the settling out of suspended carbon in the drum.

A second method of operation may be as follows:

Assuming that the still has the same capacity as in the foregoing; that is, 13,000 gallons, but that the vapor drum is of small size so that it has a liquid capacity of only 3,000 gallons, the run will be started by charging the still with-only 8,000 gallons,

the drum being empty. The still will be fired in the usual manner until a temperature of about 400F. has been attained, but during this time the distillate, consisting of water and'very light oil, willbe continuously drained out of the drum by the pipe- 20. This method-of operation has the advantage that the water and light -oil the so-called drips of the distillation processare evacuated from the system without it being necessary'to heat up the vapor drum running condition.

or any oil therein. After these drips are olf, the still may be put underpressure in the manner heretofore described and firing I continued until the still' is brought up to firing, distillate will continue to, come over from the still and to accumulate in the vapor drum until the latter has been filled, the temperature of the vapor drum being, during this time, so low that substantially no ,75 vapors will. pass to the water-cooled condenser. ,Wl1en normal conditions are estabf lished, therefore, the contents of the still will have been reduced to about 5,000 gallons, and the vapor drum will contain about-'80 3,000 gallons of oil which will be its capac-' ity up to the overflow pipe. When these conditions are established, the still will be fired at such a rate as to produce 250 gallons of distillate per hour, and feed stock will be a introduced at the rate of 350 gallons per hour, the still temperature and drum temperature remaining as described in the previous example. Running conditions will be maintained for 7 4 hours during which time tillate produced approximately 55% of this. 9.5

There will remain in the still 12,400 gallons of tar, while the drum will contain 3,000 gallons of intermediate distillate.

The method of operation last described has the advantage of giving a shorter period of preliminary firing before the still comes to its normal running condition. Thus, it has,

been stated that the so-called drips, that is, the water or lighter constituents of the charging stock may be withdrawn directly from the drum without permitting the latter to heat up, and a shorter time is, therefore, required for getting off the drips.- The relaatively small proportion of the total oil i treated during. the cycle which is present in the still at the beginning of the operation, reduces almost proportionately the time required forattaining the running condition. Nor is the saving of coal in this initial heating sacrificed in the subsequent stages of the run for the excess of the stock fed to the drum over the distillate is continuously heated as itenters the system by absorbing the latent heat of vaporization of f the fractionally condensed constituents of the outgoing vapors, thus utilizing heat energy which would Y other-wisebe dissipated to the atmosphere. In addition to these beneficial effects'I also consider it of advantage to introduce into the still, during the run of the latter, as largea proportion as possible of fresh stock,

a result which is attained in the present .instance by an operation which may be de scribed as not only feeding the still while running, but also charging it while runnlng.

During such initial 70 l have found that in the operationas de scribed in the foregoing the drum 7, containing a relatively large body of liquid with which the vapors come into intimate contact, acts as a stabilizer of the entire process,

being of the greatest aid in maintaining un1- to achieve even under laboratory conditions' This result, furthermore, is attained without the use of any sensitive automatic control apparatus, butsolely by designing the system in such a manner that it shall be inherently stable.

llt is to be particularly. noted, with respect to the detailed construction of the vapor drum 7 that the latter afi'ords an expansion chamber of considerable size at the end at whichthe vapors enter. In this chamber oportunityis afl'ordedfor the dropping out of entrained liquid particles from the vapor stream. The immediateg'eturn to the still of these unvaporized particles without un necessary cooling thereof not only conserves fuel but prevents the fouling and stoppage of the vapor pipes and orifices in the condensing system proper, the best design of the latter being to a large extent incompatible with its use as a mere separator.

While l have in the foregoing described in some detail an apparatus constructed in accordance with my invention together with the preferred method of operating the same and some variants thereof, it will be understood that this is only for the purpose of making the invention more clear and that theinven-' the invention is to be regarded as limited only by the terms of the accompanying claims in WlllCll it is my intention to claim all novelty inherent therein as broadly as is possible in view of the prior art. V I What ll claim is:

1. The improvement in the art of distil- "ling heavy oil under 7 duction therefrom of lighter oil, whichconpressure for the prolsists in bringing substantially the entire body of the oil vapors produced within the I still and while'under their pressure of production into intimate contact with a large ncense relatively stationary body of oil, maintaining the said oil body at a constant tem-. perature substantially below the temperature in the still, whereby the issuing vapors are fractionally condensed, causing oil to flow continuously from the said large body into thestill, and taking 05 and separately condensing and collecting the Vapor constitueits which escape condensation in the oil bo 2. The improvement in the art of distilling heavy oil under pressure for the proF. duction therefrom of lighter oil, which consists in causing substantially the entire body of the vapors produced within the still to bubble through a large relatively stationary body of oil, maintaining the said oil body at a constant temperature substan tially below the temperature in the still, whereby the vapors are fractionally condensed, and continuously feeding the still from the overflow from said oil body.

still and under their pressure of production into intimate contact with a large relatively stationary body of petroleumoil, maintaining the temperature of said oil body substantially below the temperature in the still, whereby the vapors are fractionally condensed, continuously introducing fresh oil into the said oil body, continuously feeding the still from the overflow. from the. said oil body, and taking off and separately condensing and collecting the vapor constituentswhich escape condensation in the said oil body.

4:. The improvement in the art of distilling heavy oil under pressure for the production therefrom of lighter oil, which consists in beginning the pressure distilling operation with an oil body in the still of a volume considerably less than the full charge thereof, andintroducing fresh oil into the still at a rate greater than the pro duction of distillate therein, so that the mass of oil. under treatment increases during the process to a volume not greater than the full charge. I

5. The improvement in the art of distilling heavy oil under pressure for the production therefrom of lighter oil, which conat a rate greater than the rate of formation of distillates from the vapors passing through the body of liquid and returning to the body of oil in the still the liquid added to said body of liquid as fresh oil and condensate.

6. The improvement in the art of distilling heavy petroleum oils under pressure for the production therefrom of lighter oil, which consists in passing thevapors issuing from the still into an expansion chamber, maintaining such expansion chamber at a temperature not substantially below that of the still, continuously returning to the still from the expansion chamber the precipitated unvaporized oil particles subjecting the vapors passing from the expansion chamber to fractional condensation, returning the condensate to the still, and taking off and separately condensing and collecting those vapors which escape condensation in the fractional condenser.

the still to drain thereto by gravity, a liquid containing chamber, means for passing vapor from said expanslon vessel into-said liquid chamber into the liquid there1n,

thereby condensing a part of said vapors, and means for conveying excess liquid from said liquid chamber to the still by gravity.

8. A petroleum distilling apparatus comprising a still, a drum mounted above the still, an overflow connection in said drum for maintaining a constant level therein, said overflow connection extending into the still below the normal liquid level therein, and a separate vapor connection communicating with the still above the liquid level therein and with the drum below the liquid level of the latter.

EDGAR M. CLARK. 

